Method for surface-finishing plastically-deformed metal liner and metal liner surface-finished by the method

Abstract

A method for surface-finishing one or more metal liners is provided, the method comprising chemical milling to remove wrinkled textures generated during the plastic deformation of the metal liners.

What is claimed is: 
     
       1. A method for surface-finishing one or more metal liners, each of which is formed by plastic deformation to be axially symmetric in shape, comprising a body section shaped to be a generally hollow cylinder with a predetermined wall thickness elongated in an axial direction; at least one dome section formed seamlessly contiguous to one end of the body section; and at least one neck section that is extruded seamlessly contiguous to the at least one dome section to form a generally narrow tube having a passage therein to channel a content, wherein the surface has wrinkled textures generated during the plastic deformation, the method comprising:
 chemical milling, 
 
       wherein the method comprises:
 housing the one or more metal liners in a rack to hold and secure the one or more metal liners therein to have a unit of the rack and the one or more metal liners housed therein; 
 first immersing the unit in a bath of an etching solution for the chemical milling for a length of immersion time; 
 showering with water the one or more metal liners of the unit while the unit is being lifted from the bath; 
 first washing with water the one or more metal liners of the unit placed outside the bath of the etching solution; 
 measuring wall thicknesses at predetermined locations of the one or more metal liners; 
 repeating the first immersing through the measuring until a predetermined smoothness is obtained, wherein the length of immersion time is adjusted according to the measured thicknesses; 
 second immersing the unit in a bath of a deoxidizing solution; 
 second washing with water the one or more metal liners of the unit placed outside the bath of the deoxidizing solution; 
 rinsing with deionized water the one or more metal liners of the unit; and 
 taking out the one or more metal liners from the rack. 
 
     
     
       2. The method of  claim 1 , wherein
 each of the one or more the metal liners has two dome sections formed seamlessly contiguous to top and bottom ends of the body section, respectively, and two neck sections that are extruded seamlessly contiguous to the two dome sections, respectively, 
 the method further comprising, during or after the first washing: 
 rotating the unit vertically by 180° to have an orientation of the unit with a top and a bottom flipped vertically; and 
 repeating the first immersing, the showering and the first washing, for the rotated unit. 
 
     
     
       3. The method of  claim 1 , wherein
 the housing includes holding the at least one neck section of each of the one or more metal liners by using at least one inwardly extended arm attached internally to the rack. 
 
     
     
       4. The method of  claim 1 , wherein
 the one or more metal liners are made of aluminum alloy; 
 the rack is made of iron; 
 the etching solution is based on sodium hydroxide; and 
 the deoxidizing solution is based on nitric acid. 
 
     
     
       5. The method of  claim 1 , wherein
 whether the predetermined smoothness is obtained is judged by the reduced thicknesses at predetermined locations based on the measurements, estimates, visual inspections of surface smoothness, or a combination thereof. 
 
     
     
       6. The method of  claim 5 , wherein
 the reduced thickness is estimated by a preset etching rate times the total immersion time.